And the American talk show host Ellen DeGeneres, who was recently informed by the New England Genealogical Society that she is a distant relative of the future queen, tweeted: “It’s a boy! So happy for my cousin Kate and the future King of England”.

Canada’s prime minister Stephen Harper also sent his “heartfelt congratulations” to the couple and the whole royal family on behalf of all Canadians.

In the capital of Ottawa, Parliament hill was illuminated with blue lights.

Australian Prime Minister Kevin Rudd said everyone wished “the Royal bub all the best”.

“I think all Australians at the bottom of their hearts with the Royal bub all the best, and certainly wish the new parents all the best as well”, Mr Rudd said.

“When a new bub comes into the world, any old day, any part of the world, it is frankly a time for rejoicing.

“To Prince Charles and Camilla, they have the delight of being grandparents, all I can say is, this is probably one of the best experiences of your life.

“And I'm sure they're going to have a wonderful time with the royal baby. And her Majesty the Queen and to the Duke of Edinburgh, the special delight of a great-grandchild.”

Media outlets worldwide were gripped by news of the birth. ABC News featured an enormous picture of the Duke and the Duchess, with the words: “William and Kate welcome the royal baby”.